4.2 - DNA and protein synthesis

What is the genome?

The complete set of genetic information

contained in the cells of an organism.

What is the proteome?

The complete set of proteins that can be

produced by a cell.

Describe the structure of messenger

RNA (mRNA).

A long, single strand. Its base sequence

is complementary to the DNA it was

transcribed from.

Suggest advantages of using mRNA

rather than DNA for translation.

● shorter & contains uracil = breaks down

quickly so no excess polypeptide forms

● single-stranded & linear = ribosome moves

along strand & tRNA binds to exposed bases

● contains no introns

Describe the structure of transfer RNA

(tRNA).

A single strand of around 80 nucleotides

that is folded over into a clover leaf

shape. On one end is an anti-codon, on

the opposite end is an amino acid

binding site.

What is produced by transcription?

mRNA.

Where does transcription take place?

In the nucleus

Outline the process of transcription.

● DNA uncoils into two strands with

exposed bases. One used as a template.

● Free nucleotides line up next to their

complementary bases, and are joined

together by RNA polymerase

What happens to mRNA after transcription?

In eukaryotic cells, pre-mRNA must be

spliced to remove introns, leaving only

the coding regions. Then it moves out of

the nucleus and attaches to a ribosome.

What is produced by translation?

Proteins

Where does translation take place?

In the cytoplasm (on ribosomes).

Outline the process of translation.

● The anti-codon of tRNA attaches to

complementary bases on the mRNA.

● Amino acids bonded to tRNA form peptide

bonds, continuing to form a polypeptide

chain until a stop codon is reached.

● This process requires ATP.